Electronically active primer layers for thermal patterning of materials for electronic devices

ABSTRACT

The present invention provides an active primer that includes an electronically active material dispersed in a binder. The active primer can be disposed between a thermal transfer donor sheet and a receptor to assist selective thermal transfer of a material from the donor sheet to the receptor to form at least a portion of an electronic device on the receptor. The binder of the active primer can be selected to improve adhesion of the transferred material to the receptor, or to enhance other transfer properties. The electronically active material of the active primer can be selected to maintain a desired level of functionality in the electronic device being patterned on the receptor.

This is a continuation of U.S. application Ser. No. 09/662,845, filedSep. 15, 2000, now U.S. Pat. No. 6,358,664. This invention relates tothermal transfer of emissive materials from donor sheets to receptorsubstrates.

BACKGROUND

Pattern-wise thermal transfer of materials from donor sheets to receptorsubstrates has been proposed for a wide variety of applications. Forexample, materials can be selectively thermally transferred to formelements useful in electronic displays and other devices. Specifically,selective thermal transfer of color filters, black matrix, spacers,polarizers, conductive layers, transistors, phosphors, and organicelectroluminescent materials have all been proposed.

SUMMARY OF THE INVENTION

Thermal transfer of some materials can be problematic, especially forhigh resolution applications and for transfer processes where adhesionof the transferred materials to the receptor upon transfer (or othersuch transfer-related properties) is an issue. To address these issues,adhesive layers, or other so-called transfer assist layers, can bedeposited on receptors or on transfer layers prior to thermal transfer.However, when transferring a material or materials to make anelectronically active device such as a transistor or an organicelectroluminescent device, the adhesive or transfer assist layer willoften be disposed between layers of the finished device. In such a case,it may be important to provide a transfer assist layer that alsoprovides functionality, or in any case does not undesirably hinderdevice operability. The present invention provides an active primerlayer that can both improve transfer properties and maintain devicefunctionality. Furthermore, the present invention contemplates an activeprimer that includes an electronically active material dispersed in abinder where the electronically active material can be selected forfunctionality (e.g., given the specific device being made, constructionof the device, materials of the device, and so on) and the binder can beselected for transfer assist properties (e.g., given the materials beingtransferred, details of the receptor substrate, and so on). The presentinvention also contemplates active primers that include polymers havingactive materials pendant to polymer backbone, that is polymersfunctionalized by covalent bonding of active materials. For the purposesof describing the present invention, the phrase “active materialdispersed in a binder” and other such descriptions of the active primerexpressly include polymers functionalized with active materials.

By way of example, active primer layers of the present invention can beuseful in improving the transfer of light emitting polymers to formorganic electroluminescent devices where the active material of theprimer layer provides a charge transport function.

In one embodiment, the present invention provides a process forpatterning a layer of an electronic device including the steps ofdisposing an active primer between a receptor substrate and a thermaltransfer donor and selectively thermally transferring a portion of atransfer layer that includes a material component of the electronicdevice from the donor to the receptor to form at least a portion of theelectronic device. The active primer includes an electronically activematerial dispersed in a binder, the binder being selected to promoteselective thermal transfer of the transfer layer to the receptor, andthe electronically active material being selected to maintainoperability of the electronic device.

In another embodiment, the present invention provides a process forpatterning a plurality of organic electroluminescent devices on areceptor. In the process, a receptor is provided that includes aplurality of anodes disposed on a surface thereof, and a thermaltransfer donor element is provided that includes a base substrate and atransfer layer. The transfer layer includes an organicelectroluminescent material. Next, an active primer is disposed betweenthe anode surface of the receptor substrate and the transfer layer ofthe donor element. The active primer includes an electronically activematerial dispersed in a binder, the binder selected to promote thermaltransfer of the transfer layer to the receptor. Next, the transfer layeris selectively thermally transferred from the donor element to thereceptor to form a pattern of the organic electroluminescent material onthe receptor. Next, a cathode material is deposited on the pattern ofthe organic electroluminescent material to form a plurality of organicelectroluminescent devices on the receptor, each of the devicesincluding in the following order one of the anodes, a portion of theactive primer, a portion of the organic electroluminescent material, anda portion of the cathode.

In yet another embodiment, the present invention provides a thermaltransfer donor element that includes a base substrate, a thermaltransfer layer capable of being selectively thermally transferred fromthe donor element to form at least a portion of an electronic device,and an active primer disposed on the thermal transfer layer as theoutermost layer of the donor element. The active primer includes anelectronically active material dispersed in a binder, the binder beingselected to promote selective thermal transfer of the transfer layer toa receptor, and the electronically active material being selected tomaintain operability of the electronic device.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may be more completely understood in consideration of thefollowing detailed description of various embodiments of the inventionin connection with the accompanying drawings, in which:

FIG. 1 is a schematic cross section of a donor sheet;

FIG. 2(a) is a schematic cross section of thermal transfer imaging of adonor sheet on a receptor with an active primer of the present inventiondisposed between the donor and the receptor; and

FIG. 2(b) is a schematic cross section of portions of one or moretransfer layers thermally transferred onto a receptor having an activeprimer layer.

While the invention is amenable to various modifications and alternativeforms, specifics thereof have been shown by way of example in thedrawings and will be described in detail. It should be understood,however, that the intention is not to limit the invention to theparticular embodiments described. On the contrary, the intention is tocover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention.

DETAILED DESCRIPTION

The present invention is believed to be applicable to thermal masstransfer of materials from a donor element to a receptor to formelectronic devices or portions thereof. In particular, the presentinvention is directed to thermal mass transfer of materials to formorganic electroluminescent devices (OLEDs) or portions thereof, andparticularly to thermal transfer of organic electroluminescentmaterials. The present invention provides a primer layer between thethermal transfer donor element and the receptor substrate, for exampleto facilitate transfer and maintain device functionality. Because thepresent invention contemplates patterning of electronic devices bythermal transfer, the active primer layer can be selected to improvetransfer properties and to maintain, or add, functionality. According tothe present invention, active primer layers disposed between donors andreceptors can include an active material dispersed in a binder, wherethe binder can be selected to promote adhesion of transferredmaterial(s) to the receptor (or to otherwise improve transferproperties) and the active material can be selected to providefunctionality. For example, the active material can be selected so thatthe primer layer performs a charge transport or charge injectionfunction in an OLED, and the binder material can be selected to improvetransfer fidelity of an organic electroluminescent material from a donorsheet to the receptor. Transfer fidelity refers to the degree to whichthe pattern of material actually transferred from donor media to areceptor matches the intended transfer pattern.

Active primers of the present invention can also allow independentselection of compatible binders (or polymers) and active materials. Theability to independently select compatible binders and active materialscan allow flexibility in designing primer layers to enable higherfidelity patterning of a wider range of materials for electronicdevices. This can be particularly useful when thermally transferringlight emitting polymers or other materials that provide functionality ina device. In some instances, it may be difficult to thermally transfersuch materials due to their physical and mechanical properties (such ashigh molecular weight, rigidity, high intra-film cohesive properties,and the like). Because such materials provide functionality, it mightnot always be desirable to modify them from their pure form in order toimprove their transferability in thermal patterning operations, althoughsuch modifications have been successful, as disclosed in co-assignedU.S. patent application Ser. No. 09/662,980 (entitled “Selective ThermalTransfer of Light Emitting Polymer Blends”). The present inventionprovides an active primer that can be chosen for its transfer assistproperties with particular transfer material(s) in mind whilemaintaining desired device functionality.

FIG. 1 shows an example of a thermal transfer donor 100 that includes abase substrate 110, an optional underlayer 112, a light-to-heatconversion layer (LTHC layer) 114, an optional interlayer 118, and atransfer layer 116. Other layers can also be present. Some exemplarydonors are disclosed in U.S. Pat. Nos. 6,114,088; 5,998,085; and5,725,989, in International Publication No. 00/41893, and in co-assignedU.S. patent application Ser. Nos. 09/473,114 and 09/474,002.

Materials can be transferred from the transfer layer of a thermal masstransfer donor element to a receptor substrate by placing the transferlayer of the donor element adjacent to the receptor and irradiating thedonor element with imaging radiation that can be absorbed by the LTHClayer and converted into heat. The donor can be exposed to imagingradiation through the donor substrate, or through the receptor, or both.The radiation can include one or more wavelengths, including visiblelight, infrared radiation, or ultraviolet radiation, for example from alaser, lamp, or other such radiation source. Material from the thermaltransfer layer can be selectively transferred to a receptor in thismanner to imagewise form patterns of the transferred material on thereceptor. In many instances, thermal transfer using light from, forexample, a lamp or laser, is advantageous because of the accuracy andprecision that can often be achieved. The size and shape of thetransferred pattern (e.g., a line, circle, square, or other shape) canbe controlled by, for example, selecting the size of the light beam, theexposure pattern of the light beam, the duration of directed beamcontact with the thermal mass transfer element, and/or the materials ofthe thermal mass transfer element. The transferred pattern can also becontrolled by irradiating the donor element through a mask.

Alternatively, a thermal print head or other heating element (patternedor otherwise) can be used to selectively heat the donor elementdirectly, thereby pattern-wise transferring portions of the transferlayer. In such a case, the LTHC layer in the donor sheet is optional.Thermal print heads or other heating elements may be particularly suitedfor patterning devices for low resolution segmented displays, emissiveicons, and the like.

The mode of thermal mass transfer can vary depending on the type ofirradiation, the type of materials and properties of the LTHC layer, thetype of materials in the transfer layer, etc., and generally occurs viaone or more mechanisms, one or more of which may be emphasized orde-emphasized during transfer depending on imaging conditions, donorconstructions, and so forth. One mechanism of thermal transfer includesthermal melt-stick transfer whereby localized heating at the interfacebetween the thermal transfer layer and the rest of the donor element canlower the adhesion of the thermal transfer layer to the donor inselected locations. Selected portions of the thermal transfer layer canadhere to the receptor more strongly than to the donor so that when thedonor element is removed, the selected portions of the transfer layerremain on the receptor. Another mechanism of thermal transfer includesablative transfer whereby localized heating can be used to ablateportions of the transfer layer off of the donor element, therebydirecting ablated material toward the receptor. Yet another mechanism ofthermal transfer includes sublimation whereby material dispersed in thetransfer layer can be sublimated by heat generated in the donor element.A portion of the sublimated material can condense on the receptor. Thepresent invention contemplates transfer modes that include one or moreof these and other mechanisms whereby the heat generated in an LTHClayer of a thermal mass transfer donor element can be used to cause thetransfer of materials from a transfer layer to receptor surface.

A variety of radiation-emitting sources can be used to heat thermal masstransfer donor elements. For analog techniques (e.g., exposure through amask), high-powered light sources (e.g., xenon flash lamps and lasers)are useful. For digital imaging techniques, infrared, visible, andultraviolet lasers are particularly useful. Suitable lasers include, forexample, high power (≧100 mW) single mode laser diodes, fiber-coupledlaser diodes, and diode-pumped solid state lasers (e.g., Nd:YAG andNd:YLF). Laser exposure dwell times can vary widely from, for example, afew hundredths of microseconds to tens of microseconds or more, andlaser fluences can be in the range from, for example, about 0.01 toabout 5 J/cm² or more. Other radiation sources and irradiationconditions can be suitable based on, among other things, the donorelement construction, the transfer layer material, the mode of thermalmass transfer, and other such factors.

When high spot placement accuracy is required (e.g., for highinformation full color display applications) over large substrate areas,a laser is particularly useful as the radiation source. Laser sourcesare also compatible with both large rigid substrates (e.g., 1 m×1 m×1.1mm glass) and continuous or sheeted film substrates (e.g., 100 μm thickpolyimide sheets).

During imaging, the thermal mass transfer element can be brought intointimate contact with a receptor (as might typically be the case forthermal melt-stick transfer mechanisms) or the thermal mass transferelement can be spaced some distance from the receptor (as can be thecase for ablative transfer mechanisms or transfer material sublimationmechanisms). In at least some instances, pressure or vacuum can be usedto hold the thermal transfer element in intimate contact with thereceptor. In some instances, a mask can be placed between the thermaltransfer element and the receptor. Such a mask can be removable or canremain on the receptor after transfer. A radiation source can then beused to heat the LTHC layer (and/or other layer(s) containing radiationabsorber) in an imagewise fashion (e.g., digitally or by analog exposurethrough a mask) to perform imagewise transfer and/or patterning of thetransfer layer from the thermal transfer element to the receptor.

Typically, selected portions of the transfer layer are transferred tothe receptor without transferring significant portions of the otherlayers of the thermal mass transfer element, such as the optionalinterlayer or the LTHC layer. The presence of the optional interlayermay eliminate or reduce the transfer of material from the LTHC layer tothe receptor and/or reduce distortion in the transferred portion of thetransfer layer. Preferably, under imaging conditions, the adhesion ofthe optional interlayer to the LTHC layer is greater than the adhesionof the interlayer to the transfer layer. In some instances, a reflectiveinterlayer can be used to attenuate the level of imaging radiationtransmitted through the interlayer and reduce any damage to thetransferred portion of the transfer layer that may result frominteraction of the transmitted radiation with the transfer layer and/orthe receptor. This is particularly beneficial in reducing thermal damagewhich may occur when the receptor is highly absorptive of the imagingradiation.

Large thermal transfer elements can be used, including thermal transferelements that have length and width dimensions of a meter or more. Inoperation, a laser can be rastered or otherwise moved across the largethermal transfer element, the laser being selectively operated toilluminate portions of the thermal transfer element according to adesired pattern. Alternatively, the laser may be stationary and thethermal transfer element and/or receptor substrate moved beneath thelaser.

In some instances, it may be necessary, desirable, and/or convenient tosequentially use two or more different thermal transfer elements to formelectronic devices on a receptor. For example, multiple layer devicescan be formed by transferring separate layers or separate stacks oflayers from different thermal transfer elements. Multilayer stacks canalso be transferred as a single transfer unit from a single donorelement. Examples of multilayer devices include transistors such asorganic field effect transistors (OFETs), organic electroluminescentpixels and/or devices, including OLEDs. Multiple donor sheets can alsobe used to form separate components in the same layer on the receptor.For example, three different donors that each have a transfer layercomprising an organic electroluminescent material that emits a differentcolor (for example, red, green, and blue) can be used to form RGBsub-pixel OLED elements for a color electronic display. Also, separatedonor sheets, each having multiple layer transfer layers, can be used topattern different multilayer devices (e.g., OLEDs that emit differentcolors, OLEDs and OFETs that connect to form addressable pixels, etc.).Typically, materials from separate donor sheets are transferred adjacentto other materials on a receptor for form adjacent devices, portions ofadjacent devices, or different portions of the same device.Alternatively, materials from separate donor sheets can be transferreddirectly on top of, or in partial overlying registration with, otherlayers or materials previously patterned onto the receptor either bythermal transfer or some other transfer method. A variety of othercombinations of two or more thermal transfer elements can be used toform a device, each thermal transfer element forming one or moreportions of the device. It will be understood other portions of thesedevices, or other devices on the receptor, may be formed in whole or inpart by any suitable process including photolithographic processes, inkjet processes, and various other printing or mask-based processes.

Referring back to FIG. 1, various layers of the thermal mass transferdonor element 100 will now be described.

The donor substrate 110 can be a polymer film. One suitable type ofpolymer film is a polyester film, for example, polyethyleneterephthalate or polyethylene naphthalate films. However, other filmswith sufficient optical properties, including high transmission of lightat a particular wavelength, as well as sufficient mechanical and thermalstability for the particular application, can be used. The donorsubstrate, in at least some instances, is flat so that uniform coatingscan be formed. The donor substrate is also typically selected frommaterials that remain stable despite heating of the LTHC layer. However,as described below, the inclusion of an underlayer between the substrateand the LTHC layer can be used to insulate the substrate from heatgenerated in the LTHC layer during imaging. The typical thickness of thedonor substrate ranges from 0.025 to 0.15 mm, preferably 0.05 to 0.1 mm,although thicker or thinner donor substrates may be used.

The materials used to form the donor substrate and an adjacentunderlayer can be selected to improve adhesion between the donorsubstrate and the underlayer, to control heat transport between thesubstrate and the underlayer, to control imaging radiation transport tothe LTHC layer, to reduce imaging defects and the like. An optionalpriming layer can be used to increase uniformity during the coating ofsubsequent layers onto the substrate and also increase the bondingstrength between the donor substrate and adjacent layers. One example ofa suitable substrate with primer layer is available from Teijin Ltd.(Product No. HPE100, Osaka, Japan).

An optional underlayer 112 may be coated or otherwise disposed between adonor substrate and the LTHC layer, for example to control heat flowbetween the substrate and the LTHC layer during imaging and/or toprovide mechanical stability to the donor element for storage, handling,donor processing, and/or imaging. Examples of suitable underlayers andmethods of providing underlayers are disclosed in co-assigned U.S.patent application Ser. No. 09/743,114, (entitled “Thermal TransferDonor Element having a Heat Management Underlayer”).

The underlayer can include materials that impart desired mechanicaland/or thermal properties to the donor element. For example, theunderlayer can include materials that exhibit a low (specificheat×density) and/or low thermal conductivity relative to the donorsubstrate. Such an underlayer may be used to increase heat flow to thetransfer layer, for example to improve the imaging sensitivity of thedonor.

The underlayer may also include materials for their mechanicalproperties or for adhesion between the substrate and the LTHC. Using anunderlayer that improves adhesion between the substrate and the LTHClayer may result in less distortion in the transferred image. As anexample, in some cases an underlayer can be used that reduces oreliminates delamination or separation of the LTHC layer, for example,that might otherwise occur during imaging of the donor media. This canreduce the amount of physical distortion exhibited by transferredportions of the transfer layer. In other cases, however it may bedesirable to employ underlayers that promote at least some degree ofseparation between or among layers during imaging, for example toproduce an air gap between layers during imaging that can provide athermal insulating function. Separation during imaging may also providea channel for the release of gases that may be generated by heating ofthe LTHC layer during imaging. Providing such a channel may lead tofewer imaging defects.

The underlayer may be substantially transparent at the imagingwavelength, or may also be at least partially absorptive or reflectiveof imaging radiation. Attenuation and/or reflection of imaging radiationby the underlayer may be used to control heat generation during imaging.

The underlayer can be comprised of any of a number of known polymerssuch as thermoset (crosslinked), thermosettable (crosslinkable), orthermoplastic polymers, including acrylates (including methacrylates,blends, mixtures, copolymers, terpolymers, tetrapolymers, oligomers,macromers, etc.), polyols (including polyvinyl alcohols), epoxy resins(also including copolymers, blends, mixtures, terpolymers,tetrapolymers, oligomers, macromers, etc.), silanes, siloxanes (with alltypes of variants thereof), polyvinyl pyrrolidinones, polyesters,polyimides, polyamides, poly(phenylene sulphide), polysulphones,phenol-formaldehyde resins, cellulose ethers and esters (for example,cellulose acetate, cellulose acetate butyrate, etc.), nitrocelluloses,polyurethane, polyesters (for example, poly(ethylene terephthalate),polycarbonates, polyolefin polymers (for example, polyethylene,polypropylene, polychloroprene, polyisobutylene,polytetrafluoroethylene, polychlorotrifluoroethylene,poly(p-chlorostyrene), polyvinylidene fluoride, polyvinylchloride,polystyrene, etc.) and copolymers (for example,polyisobutene-co-isoprene, etc.), polymerizable compositions comprisingmixtures of these polymerizable active groups (e.g., epoxy-siloxanes,epoxy-silanes, acryloyl-silanes, acryloyl-siloxanes, acryloyl-epoxies,etc.), phenolic resins (e.g., novolak and resole resins),polyvinylacetates, polyvinylidene chlorides, polyacrylates,,nitrocelluloses, polycarbonates, and mixtures thereof. The underlayersmay include homopolymers or copolymers (including, but not limited torandom copolymers, graft copolymers, block copolymers, etc.).

Underlayers may be formed by any suitable means, including coating,laminating, extruding, vacuum or vapor depositing, electroplating, andthe like. For example, crosslinked underlayers may be formed by coatingan uncrosslinked material onto a donor substrate and crosslinking thecoating. Alternatively a crosslinked underlayer may be initially formedand then laminated to the substrate subsequent to crosslinking.Crosslinking can take place by any means known in the art, includingexposure to radiation and/or thermal energy and/or chemical curatives(water, oxygen, etc.).

The thickness of the underlayer is typically greater than that ofconventional adhesion primers and release layer coatings, preferablygreater than 0.1 microns, more preferably greater than 0.5 microns, mostpreferably greater than 1 micron. In some cases, particularly forinorganic or metallic underlayers, the underlayer can be much thinner.For example, thin metal underlayers that are at least partiallyreflective at the imaging wavelength might be useful in imaging systemswhere the donor elements are irradiated from the transfer layer side. Inother cases, the underlayers can be much thicker than these ranges, forexample when the underlayer is included to provide some mechanicalsupport in the donor element.

Referring again to FIG. 1, an LTHC layer 114 can be included in thermalmass transfer elements of the present invention to couple irradiationenergy into the thermal transfer element. The LTHC layer preferablyincludes a radiation absorber that absorbs incident radiation (e.g.,laser light) and converts at least a portion of the incident radiationinto heat to enable transfer of the transfer layer from the thermaltransfer element to the receptor.

Generally, the radiation absorber(s) in the LTHC layer absorb light inthe infrared, visible, and/or ultraviolet regions of the electromagneticspectrum and convert the absorbed radiation into heat. The radiationabsorber materials are typically highly absorptive of the selectedimaging radiation, providing an LTHC layer with an optical density atthe wavelength of the imaging radiation in the range of about 0.2 to 3or higher. Optical density is the absolute value of the logarithm (base10) of the ratio of the intensity of light transmitted through the layerto the intensity of light incident on the layer.

Radiation absorber material can be uniformly disposed throughout theLTHC layer or can be non-homogeneously distributed. For example, asdescribed in co-assigned U.S. patent application Ser. No. 09/474,002,(entitled “Thermal Mass Transfer Donor Elements”), non-homogeneous LTHClayers can be used to control temperature profiles in donor elements.This can give rise to thermal transfer elements that have improvedtransfer properties (e.g., better fidelity between the intended transferpatterns and actual transfer patterns).

Suitable radiation absorbing materials can include, for example, dyes(e.g., visible dyes, ultraviolet dyes, infrared dyes, fluorescent dyes,and radiation-polarizing dyes), pigments, metals, metal compounds, metalfilms, and other suitable absorbing materials. Examples of suitableradiation absorbers includes carbon black, metal oxides, and metalsulfides. One example of a suitable LTHC layer can include a pigment,such as carbon black, and a binder, such as an organic polymer. Anothersuitable LTHC layer includes metal or metal/metal oxide formed as a thinfilm, for example, black aluminum (i.e., a partially oxidized aluminumhaving a black visual appearance). Metallic and metal compound films maybe formed by techniques, such as, for example, sputtering andevaporative deposition. Particulate coatings may be formed using abinder and any suitable dry or wet coating techniques. LTHC layers canalso be formed by combining two or more LTHC layers containing similaror dissimilar materials. For example, an LTHC layer can be formed byvapor depositing a thin layer of black aluminum over a coating thatcontains carbon black disposed in a binder.

Dyes suitable for use as radiation absorbers in a LTHC layer may bepresent in particulate form, dissolved in a binder material, or at leastpartially dispersed in a binder material. When dispersed particulateradiation absorbers are used, the particle size can be, at least in someinstances, about 10 μm or less, and may be about 1 μm or less. Suitabledyes include those dyes that absorb in the IR region of the spectrum.For example, IR absorbers marketed by Glendale Protective Technologies,Inc., Lakeland, Fla., under the designation CYASORB IR-99, IR-126 andIR-165 may be used. A specific dye may be chosen based on factors suchas, solubility in, and compatibility with, a specific binder and/orcoating solvent, as well as the wavelength range of absorption.

Pigmentary materials may also be used in the LTHC layer as radiationabsorbers. Examples of suitable pigments include carbon black andgraphite, as well as phthalocyanines, nickel dithiolenes, and otherpigments described in U.S. Pat. Nos. 5,166,024 and 5,351,617.Additionally, black azo pigments based on copper or chromium complexesof, for example, pyrazolone yellow, dianisidine red, and nickel azoyellow can be useful. Inorganic pigments can also be used, including,for example, oxides and sulfides of metals such as aluminum, bismuth,tin, indium, zinc, titanium, chromium, molybdenum, tungsten, cobalt,iridium, nickel, palladium, platinum, copper, silver, gold, zirconium,iron, lead, and tellurium. Metal borides, carbides, nitrides,carbonitrides, bronze-structured oxides, and oxides structurally relatedto the bronze family (e.g., WO_(2.9)) may also be used.

Metal radiation absorbers may be used, either in the form of particles,as described for instance in U.S. Pat. No. 4,252,671, or as films, asdisclosed in U.S. Pat. No. 5,256,506. Suitable metals include, forexample, aluminum, bismuth, tin, indium, tellurium and zinc.

Suitable binders for use in the LTHC layer include film-formingpolymers, such as, for example, phenolic resins (e.g., novolak andresole resins), polyvinyl butyral resins, polyvinyl acetates, polyvinylacetals, polyvinylidene chlorides, polyacrylates, cellulosic ethers andesters, nitrocelluloses, and polycarbonates. Suitable binders mayinclude monomers, oligomers, or polymers that have been, or can be,polymerized or crosslinked. Additives such as photoinitiators may alsobe included to facilitate crosslinking of the LTHC binder. In someembodiments, the binder is primarily formed using a coating ofcrosslinkable monomers and/or oligomers with optional polymer.

The inclusion of a thermoplastic resin (e.g., polymer) may improve, inat least some instances, the performance (e.g., transfer propertiesand/or coatability) of the LTHC layer. It is thought that athermoplastic resin may improve the adhesion of the LTHC layer to thedonor substrate. In one embodiment, the binder includes 25 to 50 wt. %(excluding the solvent when calculating weight percent) thermoplasticresin, and, preferably, 30 to 45 wt. % thermoplastic resin, althoughlower amounts of thermoplastic resin may be used (e.g., 1 to 15 wt. %).The thermoplastic resin is typically chosen to be compatible (i.e., forma one-phase combination) with the other materials of the binder. In atleast some embodiments, a thermoplastic resin that has a solubilityparameter in the range of 9 to 13 (cal/cm³)^(½), preferably, 9.5 to 12(cal/cm³)^(½), is chosen for binder. Examples of suitable thermoplasticresins include polyacrylics, styrene-acrylic polymers and resins, andpolyvinyl butyral.

Conventional coating aids, such as surfactants and dispersing agents,may be added to facilitate the coating process. The LTHC layer may becoated onto the donor substrate using a variety of coating methods knownin the art. A polymeric or organic LTHC layer is coated, in at leastsome instances, to a thickness of 0.05 μm to 20 μm, preferably, 0.5 μmto 10 μm, and, more preferably, 1 μm to 7 μm. An inorganic LTHC layer iscoated, in at least some instances, to a thickness in the range of0.0005 to 10 μm, and preferably, 0.001 to 1 μn.

Referring again to FIG. 1, an optional interlayer 118 may be disposedbetween the LTHC layer 114 and transfer layer 116. The interlayer can beused, for example, to minimize damage and contamination of thetransferred portion of the transfer layer and may also reduce distortionin the transferred portion of the transfer layer. The interlayer mayalso influence the adhesion of the transfer layer to the rest of thethermal transfer donor element. Typically, the interlayer has highthermal resistance. Preferably, the interlayer does not distort orchemically decompose under the imaging conditions, particularly to anextent that renders the transferred image non-functional. The interlayertypically remains in contact with the LTHC layer during the transferprocess and is not substantially transferred with the transfer layer.

Suitable interlayers include, for example, polymer films, metal layers(e.g., vapor deposited metal layers), inorganic layers (e.g., sol-geldeposited layers and vapor deposited layers of inorganic oxides (e.g.,silica, titania, and other metal oxides)), and organic/inorganiccomposite layers. Organic materials suitable as interlayer materialsinclude both thermoset and thermoplastic materials. Suitable thermosetmaterials include resins that may be crosslinked by heat, radiation, orchemical treatment including, but not limited to, crosslinked orcrosslinkable polyacrylates, polymethacrylates, polyesters, epoxies, andpolyurethanes. The thermoset materials may be coated onto the LTHC layeras, for example, thermoplastic precursors and subsequently crosslinkedto form a crosslinked interlayer.

Suitable thermoplastic materials include, for example, polyacrylates,polymethacrylates, polystyrenes, polyurethanes, polysulfones,polyesters, and polyimides. These thermoplastic organic materials may beapplied via conventional coating techniques (for example, solventcoating, spray coating, or extrusion coating). Typically, the glasstransition temperature (T_(g)) of thermoplastic materials suitable foruse in the interlayer is 25° C. or greater, preferably 50° C. orgreater, more preferably 100° C. or greater, and, most preferably, 150°C. or greater. In some embodiments, the interlayer includes athermoplastic material that has a T_(g) greater than any temperatureattained in the transfer layer during imaging. The interlayer may beeither transmissive, absorbing, reflective, or some combination thereof,at the imaging radiation wavelength.

Inorganic materials suitable as interlayer materials include, forexample, metals, metal oxides, metal sulfides, and inorganic carboncoatings, including those materials that are highly transmissive orreflective at the imaging light wavelength. These materials may beapplied to the light-to-heat-conversion layer via conventionaltechniques (e.g., vacuum sputtering, vacuum evaporation, or plasma jetdeposition).

The interlayer may provide a number of benefits. The interlayer may be abarrier against the transfer of material from the light-to-heatconversion layer. It may also modulate the temperature attained in thetransfer layer so that thermally unstable materials can be transferred.For example, the interlayer can act as a thermal diffuser to control thetemperature at the interface between the interlayer and the transferlayer relative to the temperature attained in the LTHC layer. This mayimprove the quality (i.e., surface roughness, edge roughness, etc.) ofthe transferred layer. The presence of an interlayer may also result inimproved plastic memory in the transferred material.

The interlayer may contain additives, including, for example,photoinitiators, surfactants, pigments, plasticizers, and coating aids.The thickness of the interlayer may depend on factors such as, forexample, the material of the interlayer, the material and properties ofthe LTHC layer, the material and properties of the transfer layer, thewavelength of the imaging radiation, and the duration of exposure of thethermal transfer element to imaging radiation. For polymer interlayers,the thickness of the interlayer typically is in the range of 0.05 μm to10 μm. For inorganic interlayers (e.g., metal or metal compoundinterlayers), the thickness of the interlayer typically is in the rangeof 0.005 μm to 10 μm.

Referring again to FIG. 1, a thermal transfer layer 116 is included inthermal mass transfer donor elements of the present invention. Transferlayer 116 can include any suitable material or materials, disposed inone or more layers with or without a binder, that can be selectivelytransferred as a unit or in portions by any suitable transfer mechanismwhen the donor element is exposed to direct heating or to imagingradiation that can be absorbed by the LTHC layer and converted intoheat.

Examples of transfer layers that can be selectively patterned fromthermal mass transfer donor elements include colorants (e.g., pigmentsand/or dyes dispersed in a binder), polarizers, liquid crystalmaterials, particles (e.g., spacers for liquid crystal displays,magnetic particles, insulating particles, conductive particles, and thelike, typically dispersed in a binder), emissive materials (e.g.,phosphors, organic electroluminescent materials, etc.), hydrophobicmaterials (e.g., partition banks for ink jet receptors), hydrophilicmaterials, multilayer stacks (e.g., multilayer device constructions suchas organic electroluminescent devices), microstructured ornanostructured layers, photoresist, metals, polymers, adhesives,binders, enzymes and other bio-materials, and other suitable materialsor combination of materials. These and other transfer layers aredisclosed in the following documents: U.S. Pat. Nos. 6,114,088;5,998,085; 5,725,989; 5,710,097; 5,693,446; 5,691,098; 5,685,939; and5,521,035; International Publication Nos. WO 97/15173, WO 99/46961, andWO 00/41893.

Particularly well suited transfer layers include materials that areuseful in making electronic devices and displays. Thermal mass transferaccording to the present invention can be performed to pattern one ormore materials on a receptor with high precision and accuracy usingfewer processing steps than for photolithography-based patterningtechniques, and for materials that are not well-suited forphotolithographic patterning (e.g., light emitting polymers), and thuscan be especially useful in applications such as display manufacture.For example, transfer layers can be made so that, upon thermal transferto a receptor, the transferred materials form color filters, blackmatrix, spacers, barriers, partitions, polarizers, retardation layers,wave plates, organic conductors or semi-conductors, inorganic conductorsor semi-conductors, organic electroluminescent layers, phosphor layers,OLEDs, organic transistors such as OFETs, and other such elements,devices, or portions thereof that can be useful in displays, alone or incombination with other elements that may or may not be patterned in alike manner.

In particularly suited embodiments, the transfer layer can include oneor more materials useful in emissive displays such as OLED displays. Forexample, the transfer layer can include a light emitting polymer, anorganic small molecule light emitter, an organic charge transportmaterial, as well as other organic conductive or semiconductivematerials. Examples of classes of light emitting polymers (LEPs) includepoly(phenylenevinylene)s (PPVs), poly-para-phenylenes (PPPs),polyfluorenes (PFs), co-polymers thereof, and blends containing theseLEPs or co-polymers. Other examples of light emitting organics includeorganic small molecule emitters, molecularly doped LEPs, light emittingorganics dispersed with fluorescent dyes, and the like. Other types ofpolymer-based emissive materials include small molecule light emittersdispersed in a polymer matrix. For example, poly(9-vinylcarbazole),commonly known as PVK, PVCz, or polyvinylcarbazole, is frequently usedas a polymeric matrix for dispersing small molecules for hybrid OLEDs.Thermal transfer of materials from donor sheets to receptors foremissive display and device applications is disclosed in U.S. Pat. Nos.6,114,088 and 5,998,085, and in International Publication 00/41893.

In at least some instances, an OLED includes a thin layer, or layers, ofone or more suitable organic materials sandwiched between a cathode andan anode. Electrons are injected into the organic layer(s) from thecathode and holes are injected into the organic layer(s) from the anode.As the injected charges migrate towards the oppositely chargedelectrodes, they may recombine to form electron-hole pairs which aretypically referred to as excitons. These excitons, or excited statespecies, may emit energy in the form of light as they decay back to aground state (see, for example, T. Tsutsui, MRS Bulletin, 22, pp. 39-45(1997)). Materials useful in OLEDs are disclosed by J. L. Segura, “TheChemistry of Electroluminescent Organic Materials”, Acta Polym., 49, pp.319-344 (1998) and by A. Kraft et al., “Electroluminescent ConjugatedPolymers—Seeing Polymers in a New Light”, Angew. Chem. Int. Ed., 37, pp.402-428 (1998).

Illustrative examples of OLED constructions include molecularlydispersed polymer devices where charge carrying and/or emitting speciesare dispersed in a polymer matrix (see J. Kido “OrganicElectroluminescent devices Based on Polymeric Materials”, Trends inPolymer Science, 2, pp. 350-355 (1994)), conjugated polymer deviceswhere layers of polymers such as polyphenylene vinylene act as thecharge carrying and emitting species (see J. J. M. Halls et al., ThinSolid Films, 276, pp. 13-20 (1996)), vapor deposited small moleculeheterostructure devices (see U.S. Pat. No. 5,061,569 and C. H. Chen etal., “Recent Developments in Molecular Organic ElectroluminescentMaterials”, Macromolecular Symposia, 125, pp. 1-48 (1997)), lightemitting electrochemical cells (see Q. Pei et al., J. Amer. Chem. Soc.,118, pp. 3922-3929 (1996)), and vertically stacked organiclight-emitting diodes capable of emitting light of multiple wavelengths(see U.S. Pat. No. 5,707,745 and Z. Shen et al., Science, 276, pp.2009-2011 (1997)).

Referring to FIG. 1, the donor element 100 can also include an optionaltransfer assist layer (not shown), most typically provided as a layer ofan adhesive or an adhesion promoter coated on the transfer layer 116 asthe outermost layer of the donor element 116. Such an optional transferassist layer can be provided in addition to the active primer layer ofthe present invention. The transfer assist layer can serve to promotecomplete transfer of the transfer layer, especially during theseparation of the donor from the receptor substrate after imaging.Exemplary transfer assist layers include colorless, transparentmaterials with a slight tack or no tack at room temperature, such as thefamily of resins sold by ICI Acrylics under the trade designationElvacite (e.g., Elvacite 2776). The transfer assist layer may alsocontain a radiation absorber that absorbs light of the same frequency asthe imaging laser or light source. Transfer assist layers can also beoptionally disposed on the receptor in addition to or instead of thoseoptionally disposed on donor elements.

The receptor substrate may be any item suitable for a particularapplication including, but not limited to, glass, transparent films,reflective films, metals, semiconductors, various papers, and plastics.For example, receptor substrates may be any type of substrate or displayelement suitable for display applications. Receptor substrates suitablefor use in displays such as liquid crystal displays or emissive displaysinclude rigid or flexible substrates that are substantially transmissiveto visible light. Examples of suitable rigid receptors include glass andrigid plastic that are coated or patterned with indium tin oxide and/orare circuitized with low temperature polysilicon (LTPS) or othertransistor structures, including organic transistors. Suitable flexiblesubstrates include substantially clear and transmissive polymer films,reflective films, transflective films, polarizing films, multilayeroptical films, and the like. Flexible substrates can also be coated orpatterned with electrode materials or transistors. Suitable polymersubstrates include polyester base (e.g., polyethylene terephthalate,polyethylene naphthalate), polycarbonate resins, polyolefin resins,polyvinyl resins (e.g., polyvinyl chloride, polyvinylidene chloride,polyvinyl acetals, etc.), cellulose ester bases (e.g., cellulosetriacetate, cellulose acetate), and other conventional polymeric filmsused as supports. For making OLEDs on plastic substrates, it is oftendesirable to include a barrier film or coating on one or both surfacesof the plastic substrate to protect the organic light emitting devicesand their electrodes from exposure to undesired levels of water, oxygen,and the like.

Receptor substrates can be pre-patterned with any one or more ofelectrodes, transistors, capacitors, insulator ribs, spacers, colorfilters, black matrix, and other elements useful for electronic displaysor other devices.

The present invention contemplates, among other things, using an activeprimer layer disposed between the donor and receptor during thermaltransfer operations to facilitate transfer of materials to formelectronic devices or portions thereof. The idea of an active primer isto provide a material or materials that can be disposed to improveadhesion and/or other transfer properties (hence the term “primer”)without destroying the operability of the electronic device or devicesbeing patterned (hence the term “active”).

To illustrate, FIGS. 2(a) and (b) show selective thermal transfer of atransfer layer 216 onto a receptor 220 where an active primer layer 222has been disposed between the transfer layer 216 and the receptor 220.Without loss of generality, FIGS. 2(a) and (b) are discussed in terms oftransferring organic electroluminescent materials, specifically lightemitting polymers, to form OLEDs. It will be recognized, however, thatthe concepts illustrated can be applied to patterning of otherelectronic devices or portions thereof. In FIG. 2(a), a laser beam 230is incident on a donor sheet that includes a substrate 210, an LTHClayer 212, an interlayer 214, and a transfer layer 216. In this case,transfer layer 216 includes a light emitting polymer. The donor is incontact with active primer layer 222 which is disposed on receptor 220.In practice, the active primer layer can be coated onto the transferlayer of the donor sheet, onto the receptor, or both. Also, the activeprimer layer can be coated to form a single continuous layer on thedonor or receptor, or the active primer layer can be patterned on thedonor or the receptor. An active primer layer can be patterned by anysuitable technique including photolithography, screen printing,selective thermal transfer, deposition through a mask, and the like.When using a patterned active primer layer, it may be desirable topattern the active primer directly onto the receptor only in those areaswhere the transfer layer is to be selectively thermally transferred.

When thermally transferring different types on materials onto receptorspatterned with active primers of the present invention, it may bedesirable to select and pattern different active primers for eachdifferent type of material being transferred. For example, when making afull color OLED display, red-emissive, blue-emissive, and green-emissiveorganic materials can be patterned in adjacent stripes on a receptorfrom separate donor elements. The receptor can be pre-patterned withactive primer stripes specifically formulated for each of the differentemissive materials being transferred. For instance, the binders of theactive primers for each emissive material transfer might be the same,but the active material in the active primers might be different andspecifically selected for performance of each emissive device beingtransferred.

Active primer layer 222 includes an active material or materialsdispersed in a binder, or matrix, material, or covalently bonded to apolymer or blend of polymers. The active material(s) are active in thattheir electronic properties are selected to maintain device operability.For example, the active materials can include electronically activemolecules, oligomers, or polymers that act as charge transporters,emitters, and/or conductors. Exemplary active materials include organicsmall molecule materials used as light emitters, dopants, and chargetransport or charge injection layer materials in OLEDs. The choice ofactive material can depend on the device type, device construction, anddevice materials. The binder material or functionalizable polymer can beselected to improve adhesion between the transfer layer material and thereceptor during selective thermal transfer. These materials can includerelatively inert (e.g., non-active) polymers such aspolymethylmethacrylates (PMMAs) or polystyrenes; conductive polymerssuch as polyanilines or polythiophenes; and/or conjugated (and oftenlight emitting) polymers such as polyparaphenylene vinylenes (PPVs) orpolyfluorenes (PFs).

Illustrative examples of emitter materials that may be useful as activematerials in active primers of the present invention include4,4′-bis(2,2-diphenylethen-1-yl)biphenyl,N,N′-bis(4-(2,2-diphenylethen-1-yl)phenyl-N,N′-bis(phenyl)benzidine, andpentaphenylcyclopentadiene. Illustrative examples of dopants that may beuseful as active materials in active primers of the present inventioninclude N,N′-dimethylquinacridone,4-(dicyanomethylene)-2-methyl-6-(julolidin-4-yl-vinyl)-4H-pyran, and3-(2-benzothiazolyl)-7-(diethylamino)coumarin. Illustrative examples ofcharge transport materials that may be useful as active materials inactive primers of the present invention include hole transporters suchas N,N′-bis(3-methylphenyl)-N,N′-diphenylbenzidine (TPD),1,1-bis((di4-toylamino)phenyl)cyclohexane, andN,N′-bis(naphthalen-1-yl)-N,N′-diphenylbenzidine and electrontransporters such as3-(biphenyl4-yl)-4-phenyl-5-t-butylphenyl-1,2,4-triazole,2-(4-t-butylphenyl)-5-(4-biphenyl-4-yl)-1,3,4-oxadiazole, andtris(8-hydroxyquinolinato)aluminum.

Examples of polymers with pendant active groups that may be useful asfunctionalizable polymers for active primers of the present inventionincludepoly(4-(m-tolylphenylamino-4′-(m-tolyl-p-vinylphenylamino)biphenyl),poly(4-vinyltriphenylamine), poly(vinylcarbazole), and their copolymerswith monomers such as styrene.

In FIG. 2(a), the laser beam 230 causes an area 232 of the LTHC layer toheat up. The selective heating of the donor effects thermal transfer ofa portion 234 of the transfer layer to the receptor 220. Active primerlayer 222 can improve adhesion of transfer layer portion 234 to thereceptor 220 so that when the donor sheet is removed from the receptor,the transfer layer portion 234 remains on the receptor and adequatelymatches the intended transfer pattern. As shown in FIG. 2(b), severalportions can be transferred from the same or separate donor sheets toform other transferred portions 236 on the same receptor 220. Althoughnot shown in FIG. 2, receptor 220 can include other layers, devices,portions of devices, or other patterns such as transistor arrays,patterned or un-patterned anodes, patterned or un-patterned chargetransport materials, patterned or un-patterned insulator ribs, patternedor un-patterned buffer layers, patterned or un-patterned color filters,patterned or un-patterned polarizers, black matrix, electronic buslines, and the like.

After transfer of the light emitting material(s), other device layerscan be deposited and/or patterned. Such other device layers can includecharge transport materials, cathode layers, and the like. Insulator ribscan also be patterned after transfer of certain device layers, andbefore deposition of a common cathode to electrically isolate adjacentdevices. Patterning of such other layers can be performed by anysuitable method including photolithography, thermal transfer, depositionthrough a mask, and the like. For OLEDs, it is often desirable toencapsulate the devices by coating the finished devices with one or morelayers that form a barrier to water, oxygen, and other elements in theenvironment to which the patterned devices may be susceptible.

EXAMPLES

The following examples illustrate the use of active primer layers inthermally transferring light emitting polymers to form OLEDs.

Example 1 Preparation of a Receptor with an Active Primer Layer

A receptor substrate having an active primer layer was prepared in thefollowing manner.

An indium tin oxide (ITO) striped substrate was spin coated at 2000r.p.m. with a buffer solution consisting ofpoly(3,4-ethylenedioxythiophene)/poly(styrene sulfonic acid) (PEDT/PSS)in de-ionized water (70:30 water to PEDT/PSS, by weight). The PEDT/PSSbuffer material was the PEDT/PSS commercially available from BayerCorporation under the trade designation Baytron P 4083. The PEDT/PSScoated substrate was heated at 110° C. on a hot plate for 5 minutes inair. The PEDT/PSS coating served as a hole injecting buffer layer in thepatterned OLEDs (see Example 4). An active primer layer was then coatedover the PEDT/PSS coating. The active primer layer was a 1:1 dispersionof bis(3-methylphenyl)N,N′dimethylbenzidine (TPD) in polystyrene. TheTPD was obtained from Aldrich Chemical Company, Milwaukee, Wis. Thepolystyrene used had a 50,000 molecular weight and was obtained fromPolysciences, Warrington, Penn. The active primer was spin coated ontothe PEDT/PSS layer out of a 1.5% weight-to-volume toluene solution.

Example 2 Preparation of Donor Sheet

A thermal transfer donor sheet having a light emitting polymer transferlayer was prepared in the following manner.

An LTHC solution, given in Table I, was coated onto a 0.1 mm thickpolyethylene terapthalate (PET) film substrate. Coating was performedusing a Yasui Seiki Lab Coater, Model CAG-150, using a microgravure rollwith 150 helical cells per lineal inch. The LTHC coating was in-linedried at 80° C. and cured under ultraviolet (UV) radiation.

TABLE I LTHC Coating Solution Parts by Component Trade DesignationWeight carbon black pigment Raven 760 Ultra⁽¹⁾ 3.88 polyvinyl butyralresin Butvar B-98⁽²⁾ 0.69 acrylic resin Joncryl 67⁽³⁾ 2.07 dispersantDisperbyk 161⁽⁴⁾ 0.34 surfactant FC-430⁽⁵⁾ 0.01 epoxy novolac acrylateEbecryl 629⁽⁶⁾ 13.18 acrylic resin Elvacite 2669⁽⁷⁾ 8.792-benzyl-2-(dimethylamino)-1-(4- Irgacure 369⁽⁸⁾ 0.89 (morpholinyl)phenyl) butanone 1-hydroxycyclohexyl phenyl ketone Irgacure 184⁽⁸⁾ 0.132-butanone 43.75 1,2-propanediol monomethyl ether acetate 26.25⁽¹⁾available from Columbian Chemicals Co., Atlanta, GA ⁽²⁾available fromSolutia Inc., St. Louis, MO ⁽³⁾available from S. C. Johnson & Son, Inc.,Racine, WI ⁽⁴⁾available from Byk-Chemie USA, Wallingford, CT⁽⁵⁾available from Minnesota Mining and Manufacturing Co., St. Paul, MN⁽⁶⁾available from UCB Radcure Inc., N. Augusta, SC ⁽⁷⁾available from ICIAcrylics Inc., Memphis, TN ⁽⁸⁾available from Ciba-Geigy Corp.,Tarrytown, NY

Next, an interlayer (formulation given in Table II) was coated onto thecured LTHC layer by a rotogravure coating method using the Yasui SeikiLab Coater, Model CAG-150, with a microgravure roll having 180 helicalcells per lineal inch. This coating was in-line dried at 60° C. and UVcured.

TABLE II Interlayer Coating Solution Parts by Component Weight SR 351 HP(trimethylolpropane triacrylate 14.85 ester, available from Sartomer,Exton, PA) Butvar B-98 0.93 Joncryl 67 2.78 Irgacure 369 1.25 Irgacure184 0.19 2-butanone 48.00 1-methoxy-2-propanol 32.00

Next, a PPV light emitting polymer was spin coated out of a 0.5%weight-to-volume toluene solution onto the cured interlayer coating. ThePPV was one commercially available from Covion Organic SemiconductorsGmbH, Frankfurt, Germany, and identified as COVION PDY 132.

Example 3 Thermal Imaging of PPV onto an Active Primer Receptor

A light emitting polymer was thermally transferred in a pattern onto areceptor having an active primer layer in the following manner.

The donor sheet prepared in Example 2 was brought into contact with thereceptor substrate prepared in Example 1. The receptor was held in arecessed vacuum frame while the donor sheet was placed in contact withthe receptor and was held in place via application of a vacuum. Thetransfer layer (PPV light emitting polymer) of the donor was contactingthe active primer layer of the receptor. Next, the donor was imagedusing two single-mode Nd:YAG lasers. Scanning was performed using asystem of linear galvanometers, with the combined laser beams focusedonto the image plane using an f-theta scan lens as part of anear-telecentric configuration. The laser energy density was 0.55J/cm^(2.) The laser spot size, measured at the 1/e² intensity, was 30microns by 350 microns. The linear laser spot velocity was adjustablebetween 10 and 30 meters per second, measured at the image plane. Thelaser spot was dithered perpendicular to the major displacementdirection with about a 100 μm amplitude. The transfer layers weretransferred as lines onto the receptor, and the intended width of thelines was about 90 μm.

The PPV transfer layer was transferred in a series of lines that were inoverlying registry with the ITO stripes on the receptor substrate. Thepatterned PPV lines were observed to be uniform and defect free over theentire substrate, which measured several centimeters in each direction.

Example 4 Preparation of an OLED

An OLED was prepared in the following manner.

Insulating ribs were patterned as stripes on top of, and positionedbetween each of, the PPV lines patterned onto the receptor as preparedin Example 3. The insulating ribs were patterned by laser inducedthermal imaging of an insulating, highly filled thermoset polymerformulation from a donor element to the receptor prepared in Example 3.The insulating ribs as transferred were about 1.6 microns high andoverlapped the PPV lines by about 10 microns on each side. Next, a 400Angstrom thick calcium coating was vapor deposited over the insulatingribs and PPV stripes. Next, a 4000 Angstrom thick aluminum coating wasvapor deposited over the calcium coating. The calcium/aluminumconstruction served as a double layer cathode in the OLED. The insulatorribs maintain electrical isolation between OLED devices. The result wasa series of patterned OLEDs on the glass receptor, each OLED includingan ITO anode, a PEDT/PSS buffer layer, an active primer layer thatfunctioned as a hole transport layer and transfer assist layer, a lightemitting polymer layer, and a common double layer cathode isolated byinsulator ribs positioned between the OLEDs. Upon application of a biasvoltage across the anode and cathode, bright electroluminescence wasobserved from each of the patterned OLEDs.

The present invention should not be considered limited to the particularexamples described above, but rather should be understood to cover allaspects of the invention as fairly set out in the attached claims.Various modifications, equivalent processes, as well as numerousstructures to which the present invention may be applicable will bereadily apparent to those of skill in the art to which the presentinvention is directed upon review of the instant specification.

Each of the patents, patent documents, and publications cited above ishereby incorporated into this document as if reproduced in full.

What is claimed is:
 1. A process for making an electronic devicecomprising the steps of: disposing an active primer between a receptorsubstrate and a thermal transfer donor; disposing a transfer assistlayer on the active primer; and selectively thermally transferring aportion of a transfer layer comprising a material component of theelectronic device from the donor to the receptor substrate to form atleast a portion of the electronic device, wherein the active primercomprises a light emitting material dispersed in a binder, the binderbeing selected to promote selective thermal transfer of the transferlayer to the receptor.
 2. The process of claim 1, wherein the activeprimer comprises a charge transport material.
 3. The process of claim 1,wherein the active primer comprises an electron transport material. 4.The process of claim 1, wherein the electronic device is an organicelectroluminescent device.
 5. The process of claim 1, wherein thematerial component of the electronic device comprises an organicelectroluminescent material.
 6. The process of claim 1, whereindisposing the active primer between the donor and the receptor substratecomprises disposing the active primer on the receptor substrate.
 7. Theprocess of claim 1, wherein disposing the active primer between thedonor and the receptor comprises disposing the active primer on thetransfer layer of the donor.
 8. The process of claim 1, wherein thetransfer assist layer further comprises radiation absorbers.
 9. Theprocess of claim 1, wherein the active primer and transfer assist layersare disposed on the receptor substrate prior to selectively thermallytransferring a portion of the transfer layer.
 10. A process for makingan electronic device comprising the steps of: disposing an active primerbetween a receptor substrate and a thermal transfer donor; disposing atransfer assist layer on the active primer; and selectively thermallytransferring a portion of a transfer layer comprising a materialcomponent of the electronic device from the donor to the receptorsubstrate to form at least a portion of the electronic device, whereinthe active primer comprises a hole transport material dispersed in abinder, the binder being selected to promote selective thermal transferof the transfer layer to the receptor.
 11. The process of claim 10,wherein the electronic device is an organic electroluminescent device.12. The process of claim 10, wherein the material component of theelectronic device comprises an organic electroluminescent material. 13.The process of claim 10, wherein disposing the active primer between thedonor and the receptor substrate comprises disposing the active primeron the receptor substrate.
 14. The process of claim 10, whereindisposing the active primer between the donor and the receptor comprisesdisposing the active primer on the transfer layer of the donor.
 15. Theprocess of claim 10, wherein the transfer assist layer further comprisesradiation absorbers.
 16. The process of claim 15, wherein the activeprimer and transfer assist layers are disposed on the receptor substrateprior to selectively thermally transferring a portion of the transferlayer.
 17. A process of making an electronic device comprising the stepsof: disposing an active primer on a receptor substrate; disposing atransfer assist layer on the active primer; and selectively thermallytransferring a portion of a transfer layer comprising a materialcomponent of the electronic device from the donor to the receptorsubstrate having the active primer layer and transfer assist layerdisposed thereon to form at least a portion of the electronic device,wherein the active primer comprises an electronically active materialdispersed in a binder, the binder being selected to promote selectivethermal transfer of the transfer layer to the receptor, and theelectronically active material being selected to maintain operability ofthe electronic device.
 18. The process of claim 17, wherein theelectronically active material of the active primer comprises a chargetransport material.
 19. The process of claim 17, wherein theelectronically active material of the active primer comprises a holetransport material.
 20. The process of claim 17, wherein theelectronically active material of the active primer comprises anelectron transport material.
 21. The process of claim 17, wherein theelectronic device is an organic electroluminescent device.
 22. Theprocess of claim 17, wherein the material component of the electronicdevice comprises an organic electroluminescent material.
 23. The processof claim 17, wherein the transfer assist layer further comprisesradiation absorbers.
 24. A process for patterning a plurality of organicelectroluminescent devices on a receptor comprising the steps of:providing a receptor comprising a plurality of first electrodes disposedon a surface thereof and a buffer material coated on the firstelectrodes; providing a thermal transfer donor element comprising a basesubstrate and a transfer layer, the transfer layer comprising an organicelectroluminescent material; disposing an active primer between thesurface of the receptor and the transfer layer of the donor element, theactive primer comprising an electronically active material dispersed ina binder, the binder selected to promote thermal transfer of thetransfer layer to the receptor; selectively thermally transferring thetransfer layer from the donor element to the receptor to form a patternof the organic electroluminescent material on the receptor; anddepositing at least one second electrode on the pattern of the organicelectroluminescent material to form a plurality of organicelectroluminescent devices on the receptor, each of the devicesincluding in the following order one of the first electrodes, the buffermaterial, a portion of the active primer, a portion of the organicelectroluminescent material, and a portion of the at least one secondelectrode.
 25. The process of claim 24, wherein the step of depositingthe at least one second electrode comprises depositing a common secondelectrode.
 26. The process of claim 24, wherein the organicelectroluminescent material comprises a light emitting polymer.
 27. Theprocess of claim 24, wherein the organic electroluminescent materialcomprises a small molecule light emitter.
 28. The process of claim 24,wherein the small molecule light emitter is disposed in a polymermatrix.